The invention relates generally to the field of seals and more particularly, to systems and methods for achieving pressure balanced seals between elements having relative motion, including axial motion.
Piston rings have been widely used in gas turbine engines between a piston with axial movement and a stationary chamber to prevent leakage from a section with high pressure into a section of low pressure. This same pressure acts to urge the ring against the piston and cause frictional loading. Since, during the start up process of a gas or steam turbine, varying pressure levels may be present, the resultant pressure acting on the piston ring can vary to a great extent. As the pressure increases, the resultant friction between the piston ring and the piston increases.
There is, therefore, a need to develop more effective techniques to reduce friction between elements having relative axial motion in turbines.